1. Field
The present invention relates generally to radiation treatment, and more particularly to calibrating systems to be used during such treatment.
2. Description
Conventional radiation treatment typically involves directing a radiation beam at a tumor in a patient to deliver a predetermined dose of treatment radiation to the tumor according to an established treatment plan. A suitable radiation treatment device is described in U.S. Pat. No. 5,668,847, issued Sep. 16, 1997 to Hernandez, the contents of which are incorporated herein for all purposes.
Healthy tissue and organs are often in the treatment path of the radiation beam during radiation treatment. The healthy tissue and organs must be taken into account when delivering a dose of radiation to the tumor, thereby complicating determination of the treatment plan. Specifically, the plan must strike a balance between the need to minimize damage to healthy tissue and organs and the need to ensure that the tumor receives an adequately high dose of radiation. In this regard, cure rates for many tumors are a sensitive function of the radiation dose they receive.
Treatment plans are therefore designed to maximize radiation delivered to a target while minimizing radiation delivered to healthy tissue. If the radiation is not delivered exactly as required by the treatment plan, the goals of maximizing target radiation and minimizing healthy tissue radiation may not be achieved. More specifically, errors in radiation delivery can result in low irradiation of tumors and high irradiation of sensitive healthy tissue. The potential for mis-irradiation increases with increased delivery errors.
To ensure that radiation will be delivered to a proper area, a light field is used to indicate the position of a field within which radiation will be delivered. In particular, light is projected onto a patient to create a light field and an operator determines whether the light field delineates an area to which radiation is to be delivered according to a treatment plan. Accordingly, the light field is assumed to be located at a same position as a radiation field within which radiation will be delivered during radiation treatment.
Delivery errors may occur if the light field is not located at a same position as the subsequently-produced radiation field. Accordingly, it is necessary to verify that the position of the light field accurately represents a position of the radiation field. Conventionally, this verification is performed by illuminating X-ray film with the light field, marking the film at the edges of the light field, exposing the film to radiation, and comparing the location of the radiation field as appearing on the exposed film with the location of the marks. This system is unacceptably susceptible to the radiation field penumbra, the brightness and blurriness of the light field, and to human error in marking the film and measuring the difference in the fields.
Other systems to verify congruence between the light field and the radiation field have been proposed by Luchka et al, xe2x80x9cAssessing radiation and light field congruence with a video-based electronic portal imaging devicexe2x80x9d, Med. Phys 23 (7), July 1996, pgs 1235-1252, by Kirby, xe2x80x9cA multipurpose phantom for use with electronic portal imaging devicesxe2x80x9d, Phys. Med. Biol. 40, 1995, pgs. 323-334, and by others, but none of these systems provides desirable accuracy and efficiency.
It would therefore be beneficial to provide a system and method to efficiently and effectively verify congruence between a light field and a radiation field used for radiation treatment. When used in conjunction with conventionally-designed treatments, more accurate congruence reduces the chance of harming healthy tissue. More accurate congruence also allows the use of more aggressive treatments. Specifically, if a margin of error in field congruence is known to be small, treatment may be designed to safely radiate a greater portion of a tumor with higher doses than in scenarios where the margin of error is larger.
To address at least the above problems, some embodiments of the present invention provide a system, method, apparatus, and means to determine congruence of a light field and a radiation field through acquisition of first electronic image data representing a light field produced by a light emitter, acquisition of second electronic image data representing a radiation field produced by a treatment radiation emitter, and determination of a congruence between the light field and the radiation field based on the first data and the second data.
In some embodiments, the present invention provides acquisition of first electronic image data representing a phantom located at a first position and illuminated by light emitted by a light emitter, acquisition of second electronic image data representing the phantom located at the first position and irradiated by treatment radiation emitted by a treatment radiation emitter, normalization of the first electronic image data and the second electronic image data to account for differences in divergence properties of the emitted light and the emitted treatment radiation, generation of superimposed electronic image data based on the first normalized electronic image data and the second normalized electronic image data, determination of a distance between a location of a hole of the phantom as represented by the first normalized electronic image data and a location of the edge of the phantom as represented by the second normalized electronic image data based on the superimposed electronic image data, and determination of congruence of a light field produced by the light emitter and a treatment radiation field produced by the treatment radiation emitter based on a difference between the distance and an actual corresponding distance between the hole and the edge of the phantom.
According to some embodiments, the present invention provides acquisition of first waveforms representing a phantom located at a first position as illuminated by light emitted by a light emitter, acquisition of second waveforms representing the phantom located at the first position as irradiated by treatment radiation emitted by a treatment radiation emitter, normalization of the first waveforms and the second waveforms to account for differences in divergence properties of the emitted light and the emitted treatment radiation, determination of a first location of a hole of the phantom based on the first normalized waveforms, determination of a second location of the hole of the phantom based on the second normalized waveforms, and determination of the congruence between the light field and the radiation field based on a difference, if any, between the first location and the second location.
In some aspects, the present invention provides acquisition of first electronic image data representing a light field produced by a light emitter, acquisition of second electronic image data representing a radiation field produced by a treatment radiation emitter, acquisition of first reference electronic image data representing a reference light field produced by the light emitter, acquisition of second reference electronic image data representing a reference radiation field produced by the treatment radiation emitter, determination of a first location of a hole of the phantom based on the first reference electronic image data, determination of a second location of the hole of the phantom based on the second reference electronic image data, determination of a third location of the hole of the phantom based on the first electronic image data, determination of a fourth location of the hole of the phantom based on the second electronic image data, and comparison of a distance between the first location and the second location with a distance between the third location and the fourth location.
In still other aspects, provided are acquisition of first reference electronic image data representing a reference light field produced by a light emitter, the first reference electronic image data comprising third waveforms representing a phantom as illuminated by the reference light field, acquisition of second reference electronic image data representing a reference radiation field produced by a treatment radiation emitter, the second reference electronic image data comprising fourth waveforms representing the phantom as irradiated by the reference radiation field, acquisition of first electronic image data representing a light field produced by the light emitter and comprising first waveforms representing the phantom as illuminated by the light field, acquisition of second electronic image data representing a radiation field produced by the treatment radiation emitter and comprising second waveforms representing the phantom as irradiated by the radiation field, comparison of a location of a hole of the phantom according to the first waveforms with a location of the hole according to the third waveforms, and comparison of a location of the hole of the phantom according to the second waveforms with a location of the hole according to the fourth waveforms.
The present invention is not limited to the disclosed embodiments, however, as those of ordinary skill in the art can readily adapt the teachings of the present invention to create other embodiments and applications.